菌核菌

The presence of spores in S. Rolfsii has not been proved with the samples of foreign origin and therefore the fungs generally is known as sterile. But the formation of spores is rightly expected referring to other fungi similar to it. In 1919 SAWADA in Formosa found the spores in the fungus which he obtained from a diseased camphor tree. He referred the fungus to Hypochnus centrifugus in respect to the form and size of the spores, and also considered the names of H. Solani and H. Cucumeris as its synonyms. As to his judgement the argument has arisen and especially the materials which he used as S. Rolfsii remains in question. The present work was undertaken to discover the spores of the fungus and to make clear the genetic relationships of the fungus to H. centrifugus, H. Solani and H. Cucumeris. In addition the effect was also made to clear the specific relationship of the fungus to S. coffeicolum. To these ends a thorough comparative study of morphology and cultural features was made. The cultures of S. Rolfsii employed in this work, 33 strains in number, represented the strains from Japan, Korea, the United States of America, Philippines, Java and West Indies, widely separated geographically. The cultures of H centrifugus was received from Formosa and those of H. Solani and S. coffeicolum from Holland ; those being considered as authentic type cultures of the fungi. During summer of 1925 the writer discovered the spores in three strains of the fungus, two from Japan and other from America. Those strains had been inoculated on the crown of sugar beet and the stem of conjak plant (Amorphophallus Konjac). From the cultural and morphological studies, especially in the form and size of spores, the writer is inclined to believe that the fungus is quite identical with H. centrifugus and therefore H. centrifugus (LEV.) TUL should be applied to the perfect form of S. Rolfsii. As to the relationship of H. Solani to H. centrifugus it is regarded that they are different in color of mycelia and activity of forming sclerotia, and moreover that the sterile form of H. Solani is referable to Rhizoctonia Solani as proved by DUGGAR. Also as to H. Cucumeris it is assumed that this is not referable to H. centrifugus but to H. Solani. S. coffeicolum established by STAHEL is proved to group into S. Rolfsii as a strain by comparative study of cultural features. The results obtained lead briefly to conclude as follows: Sclerotiumn Rolfsii SACC. ＝ Hypochnus centrifugus (LEV.) TUL. : Rhizoctonia Solani KUHN ＝ H. Solani PRILL. et DELACR. (＝ Corticium vagum B. et C.)≒ H. Cucurneris FR.